Power translating device



July 27, 1937. J. SLEPIAN ,0

POWER TRANSLATING DEVICE Original Filed Dec. 13, 1923' 2 Sheets-Sheet lFYgJ.

WITNESSES: INVENTOR Vr /Mz Jose oh Slepian July 27, 1937. J. SLEPIAN2,088,490

POWER TRANSLATING DEVICE Original Filed Dec. 15, 1923 2 Sheets-Sheet 2Fig.3. 42 w W154 Time Time v l x "#55 Volts Volts 'WITNESSES: INVENTOR VM n Jo; eph Slepian UNITED STATES PATENT OFFICE 2,088,490 POWER TRANSLATING DEVICE Joseph Slepian,

inghouse a corporation of Pennsylvania December 13, 1923, Serial d andthis application De- Original application No. 680,396. Divide cembcr 14,1934, Serial No.

My invention relates to electric translating ap- 15 Claims.

paratus and it has particular relation to translating apparatus of thetype utilized in inductive heating systems.

The present application is adivision of my copending application, SerialNo. 680,396, filed December 13, 1923.

It is an object of my invention to provide inductive heating apparatus,the energy for which shall be supplied from a direct current powerAnother object of my invention is to provide inductive heatingapparatus, of the type wherein alternating current of a frequency withinthe intermediate range is supplied to the heating coil, that shall becapable of excitation from a low frequency power source or from a directcurrent power source.

More specifically stated, it

invention to provide inductive is an object of my heating apparatusdevoid of mechanical converters wherein the inductive heating coil issupplied with current of intermediate frequency while the power supplyis either direct current or of low frequency.

According to my invention heating apparatus in which or the current oflow alternating current of I provide inductive the direct currentfrequency is converted into the proper frequency by the operation of aplurality of mercury are discharge devices, the excitation of which iscon.- trolled by grids or starting electrodes.

With the foregoing and my invention consists in the cults, and methodsof operation illustrated in the acwherein,

claimed hereinafter and companying drawings,

other objects in view,

arrangements, cirdescribed and Figure 1 is a diagrammatic view showingan embodiment of my invention.

Fig. 2 is a diagrammatic view showing a modification of my invention.

Fig. 3 is a diagrammatic view illustrating the operation of the systemin Fig. 2; and,

Fig. 4 is a diagrammaticview showing a modification of Fig. 1.

In the apparatusrshown in Fig.

showing curves shown 1, alternating current is supplied t6"an inductiveheater 16 in the load circuit 4, comprising a shunt excited I from adirect current source direct current generator 14, through transformerwindings 5 and 6 and mercury arc discharge devices or rectifiers i and8. The transformer windings 5 and 6 are provided with end terminals land H, respectively, and a common neutral terminal 12. The

end terminal H is connected to the heating coil Pittsburgh, Pa.,assignor to West- Electric & Manufacturing Company,

200 of the inductive heater 16 through a capacitor 11, the other endterminal I0 being connected to the remaining terminal of the heatingcoil. The intermediate terminal I! is connected to the positive terminall3 of the direct current source.

A stabilizing inductance l5 may be connected in series with the directcurrent source 4 to maintain approximately constant current flow fromthe generator independently of the changes in the circuit relations 'ofthe translating apparatus. The stabilizing inductor is connected, in thepreferred practice of my invention, between the negative terminal 23 andthe common junction point of the cathodes 28 and 2| of the dischargedevices 1 and 8. A commutating capacitor 52 is connected between theterminals l0 and II of the auto-transformer 5-6.

The mercury arc rectifiers 1 and 8 comprise evacuated envelopes l6 andI1, respectively, having anodes l8 and 19, respectively, and mercurycathodes 28 and 2|, respectively. The anodes l8 and i9 are connected tothe terminals l0 and II, respectively, of the transformer windings 5 and6. Each rectifier 1 and 8 is provided with a starting electrode 53 whichis actuated by means of an ignition transformer 55 having a secondarywinding connected between the ignition electrode 53 and the mercurycathode of the rectifier and having a primary winding which is connectedto a source 56 of pulsating direct current through a distributor 51.

The distributor 51 comprises a plurality of annularly disposed contactmembers 58 which are alternately connected to two bus conductors 59 and80, respectively. The latter are connected by means of conductors 62 and63 to proper terminals of the primary windings of the ignitiontransformers, the other terminals of the ignition transformers beingconnected to a common conductor 64 leading to one terminal of a battery65 constituting the source of supply of the pulsating direct current.The other terminal of the battery 65 is connected, through aninterrupter 66 by a brush 61, to a distributor arm 69 which is rotatedby a motor not shown in the drawings. The distributor arm 69 alternatelymakes contact with the several contact members 58 leading to therespective ignition transformers and alternately starts the mercury arcrectiflers "I and 8.

The interrupter 68 consists of a pair of quickbreak contacts H shuntedby condenser 12. One of the contacts II is mounted upon a flexible armI3 which is biased to an open position by a spring 14. A toothed cam 15is rotated at a high 55 speed and closes and releases the quick-breakcontacts 1| at a high rate.

The alternate closing and opening of the quickbreak contacts 1I sends apulsating direct current 5 through the primary winding of the one or theother of the ignition transformers 55 during the short interval of theengagement of the distributor arm 9 with a contact member 58. Thepulsating direct current induces a high potential in the secondarywinding of the ignition transformers and impresses upon the startingelectrode 53 a high unidirectional potential with respect to the mercuryelectrode causing a discharge therebetween. The asymmetric orunidirectional quality of the induced potential results from the quickinterruption and the relatively slow establishment and building up ofthe current in'the circuit including the interrupter 66.

In the operation of the apparatus illustrated in Fig. 1, the control ofthe current fiow through the rectifiers is effected by the operation ofthe starting electrode 53. Assume that a current is flowing from thepositive terminal I 3 of the direct-current source and the rectifier 1is energized. The current divides at the middle transformer-terminal I2into two portions, one portion flowing directly through the transformerwinding 5, and the other'portion flowing through the transformer winding6 and the load circuit I to the end terminal I 0. It then flows. throughthe rectifier 1 and the conductor 19 to the negative terminal 23 of thedirect-current generator I4. The distributing arm 69 is at the same timein the position shown in the drawings. The commutating condenser 52 ischarged to a potential corresponding to the direction of flow of currentinto the load, that is, opposite to the voltage pressed thereon by thedirect-current source II.

In the course of rotation, the distributing contact arm 69 energizes theignition transformer of the formerly non-conducting rectifier I, causinga discharge between the starting electrode 53 and the mercury cathode2|. The rectifier 8 45 thereupon becomes conducting and the current fromthe direct-current generator I4 is diverted thereto by the commutatingaction of the discharge current of the commutating condenser 52, thecurrent through the rectifier 1 being 50 simultaneously reduced to zero.The mercuryarc rectifier I thereupon becomes non-conducting and thecircuit therethrough is interrupted, while the current now flows throughthe transformer winding in the opposite direction. This 55 cycle repeatsitself alternately in accordance with the operation of the ignitiondevice. By regulating the speed of the distributor-51, the frequency ofthe generated alternating currents may be controlled.

In the modification shown in Fig. 2 the fiow of current through a doublewave mercury rectifier is controlled by means of grids disposed in thespace current paths of the rectifier. The two anodes II! and I I6 of therectiflers are connected 65 to the two end terminals III and II of atransformer having two windings 5 and 6 and provided with a commonmiddle terminal I2 leading to a positive terminal I3 of the directcurrent generator I4. The mercury electrode III of the 70 rectifier ispermanently connected to the negative terminal 22 of the direct-currentgenerator I4. I

Two grids III and I I! are provided in the two rectifier paths leadingbetween the mercury Tl cathode H1 and the two anodes H5 and IIS, for

the rectifier arm II5 so controlling the rectifying action andconductivity of the paths as to utilize thedirect current flowing fromthe direct-current generator I4 to supply power to the inductive heatingcoil I52 which is connected to the two end terminals III and I I in ananalogous manner to the coil 200, the coil I52 being connected to theterminal I I through a capacitor I53.

The control potentialis provided for the discharge device by utilizlng amaster oscillator. The mercury cathode II! is connected through abiasing battery I to a common terminal 2 of two secondary transformerwindings I43 and I leading through current limiting resistors I21 to thegrids H8 and I I 9 respectively. 'The secondary windings I43 and I ofthe grid control transformer cooperate with a primary transformerwinding I45 which is included in an oscillating circuit with a condenser6. A threeelectrode tube I41 is connected in a circuit including asource of electromotive force, such as a battery I48, across thecondenser I 46. The grid I49 of the three-electrode tube I I1 isconnected, through a feed-back coil I50, to the filament and serves 'toproduce sustained oscillations in the circuit including the transformerwinding Ill and the condenser I46.

The system illustrated in Fig. 2 is particularly well adapted forproducing high-frequency currents such as are utilized in radioapplications or for certain industrial purposes such as inductionfurnaces. I have illustrated an induction furnace comprising a crucibleI5I surrounded by an inducing coil I52 which is connected in'series witha condenser I 53 across the terminals III and I I of the transformerwindings 5 and 6.

To illustrate the operation of the system shown in Fig. 2, I ,havereproduced, in Fig. 3, oscillographic records obtained during theoperation thereof. Curve I54 shows the voltage across as a function oftime; curve I55 shows the voltage across the ,rectifler arm IIG as afunction of time; curve I56 shows the voltage between the anodes H5 andH6 as a function of time; curve I51 shows the current through thetransformer winding 5 and curve I58 shows the current through thetransformer winding 6 as a function of time; and curve I59 shows thevoltage between the grid H8 and the mercury cathode I I1 as a functionof time. In determining the direction of the voltage in the abovediagrams, it has been assumed that the voltage in the direction of thearrow I 60 from the middle terminal I2 through the anode H6, cathode II1 and anode II5 back to the neutral terminal I2 is positive. Indetermining the direction of flow of current it has been assumed that acurrent flowing in the transformer windings 5 and 6 in the directionfrom right to left, that is from the end terminal II to the end terminalI0, is positive.

As will be seen from the above-described curves, the voltage across therectifier arms pulsates from a low value, corresponding to the voltagedrop of the rectifier when the arm is conducting, to a full valuecorresponding to the opencircuit conditions. The current in thetransformer winding 5 leading to the conducting rectifier arm increasesarm is conducting, while the current through the transformer winding}leading to the nonconducting arm of the rectifier decreases. The voltagewhich appears across the two terminals III and II of the transformerwindings 5 and 6, and. which is also the voltage across the two duringthe period that the rectifier anodes H and H8, corresponds to the changein flux attendant upon the increase in the current of one transformerwinding and the decrease of the current in the other transformer 5winding, both effects adding to each other since the direction of thecurrents are opposite. As seen from the above diagrams the currentflowing from the direct-current source is divided into two approximatelyequal portions pulsating around mean values. The sum of both currents isapproximately constant and corresponds to the total current flowing fromthe direct-current sourc'e.

It may thus be seen that only approximately half of the current flowingfrom the direct-current generator 14 flows into the alternating-currentload circuit. The energy corresponding to the other half of thedirect-current flow is utilized in raising the potential across the loadcircuit to approximately twice the potential ofthe directcurrentgenerator, by a transformer action in the windings 5 and 6. It is tothis end that the windings 5 and 6 are preferably arranged in inductiverelation to each other although my system would also operate with twoseparate transformers or coils.

The apparatus shown in Fig. 4 is similar to the apparatus shown in Fig-1 except that a transformer with separate coils 5-6 and ISO issubstituted for the auto-transformer specifically shown in the latterview.

Although I have shown and described certain specific embodiments of myinvention, I am fully aware that many modifications thereof arepossible. My invention, therefore, is not to be restricted' exceptinsofar as is necessitated by the prior art and b'y-the spirit of theappended claims.

I claim as my invention:

1. An electric heating system including an in- 40 ductor coil, a pair ofarc rectifiers inductively coupled together by said inductor coil, meansfor successively rendering said rectifiers alternately conducting andnon-conducting, and a condenser connected between the circuits of saidrectifiers 45 for interrupting the current flowing in one rectifiersubstantially immediately after the other rectifier is made conductive.

2. In an electric induction furnace having an inductor coil thecombination of a plurality of 50 grid controlled arc rectifiers, acapacitor, a capacitor charging circuit including one of saidrectifiers, a capacitor discharging circuit including another of saidrectifiers, and an alternating current circuit including said inductorcoil common 55 to said charging and discharging circuits.

3. In an electric induction furnace provided with an inductor coil, thecombination of a plurality of arc rectifiers, each provided with a gridfor controlling the starting of current between 60 its cathode andanode, a capacitor, capacitor charging and discharging circuitscontrolled by said rectifiers, means arranged to produce in each of saidcircuits 2. countervoltage which is dependent on the current in theother of said circuits,

an alternating circuit including said inductor coil common to saidcharging and discharging circuits'.

4. Inductive heating apparatus including the combination of a currentconductive means for inducing heating currents, a plurality of electricrectifiers, a capacitor, a capacitor charging circuit including one ofsaid rectiflers, a capacitor discharging circuit including another ofsaid rec- 75 tifiers, and an'alternating current circuit including saidcurrent conducting means common. to said charging and dischar ngcircuits.

5. Inductive heating apparatus including the combination of an inductorcoil for inducing heating currents, a plurality of electric rectifiers,a capacitor, a capacitor charging circuit including one of saidrectifiers, a capacitor discharging circuit including another of saidrectifiers, and an alternating current circuit including said inductorcoil common to said charging and discharging circuits, the said inductorcoil inductively coupling together said charging and dischargingcircuits.

6. In an induction furnace having a charge containing crucible and aninductor coil, the combination of a plurality of grid controlled arcrectifiers inductively coupled together by said coil, a capacitor,connections for connecting said capacitor with said coil to produce asubstantially resonant circuit, a variable frequency source of supplyfor said grids, and means for varying said frequency so as to maintainsaid circuit substantially resonant. v

"I. In an induction furnace provided with an inductor coil, thecombination of a plurality of arc rectiflers, each provided with a gridfor controlling the starting of current between its cathode and anode,means for generating a control voltage for said gridameans for varyingthe frequency of said control voltage, a capacitor, ca-

pacitor charging and discharging circuits controlled by said rectiflers,means arranged to produce in each of said circuits a countervoltagewhich is dependent on the current in the other of said circuits, analternating circuit including said inductor coil common chargingcircuits.

8. Apparatus for heating an element comprising an inductor coil forinducing heating currents to said charging and disin said element, afirst discharge device for supplying current pulsations of one polaritytosaid inductor coil, a second discharge device for supplying currentpulsations of the opposite polarity to said inductor coil and meansindependent of said coil for predetermining the frequency of saidpulsations.

9. Apparatus for heating an element comprising an inductor coil forinducing heating currents in said element, a discharge device having acontrol electrode and a plurality of principal electrodes for supplyingcurrent pulsations to said inductor coil and means independent of saidcoil for impressing potentials between said control electrode and said.principal electrodes to predetermine the frequency of said pulsations.

10. Apparatus for heating an element comprising an inductor coil forinducing heating currents in said element, a first discharge devicehaving a control electrode and a plurality of principal electrodes forsupplying current pulsations of one polarity to said inductor coil, asecond discharge device having a control electrode and a plurality ofprincipal electrodes for supplying current pulsations of the oppositepolarity to said inductor coil and means independent of said coil forimpressing potentials between the control electrode and the principalelectrodes of each of said discharge devices to predetermine thefrequency of said pulsations.

11. Apparatus for heating an element comprising an inductor coil forinducing heating currents in said element, a discharge device forsupplying current pulsations to said inductor coil and means independentof said coil and including a master oscillation generator forpredetermining the frequency of said pulsations.

12. Apparatus according to claim 10 characterized by that the means forpredetermining the irequency oi the pulsations includes a masterosciliation generator common to both said discharge devices.

13. Apparatus for heating an element comprising an inductor coil forinducing heating currents in said element, a discharge device forsupplying current pulsations to said inductor coil and means independentof said coil and including a master oscillation generator of the typeincorporating a high-vacuum discharge device for predetermining theirequency of said pulsations.

14. Apparatus for heating an element comprising an inductor coil forinducing heating currents in said element, a discharge device forsupplying current pulsations to said inductor coil quency of saidpulsations.

device having a control electrode and a plurality 10 of principalelectrodes for supplying current pulsations of the opposite polarity totrol electrode and the principal electrodes of each of said dischargedevices to predetermine the ire- JOSEPH SLEPIAN.

